ATOI(3P)                                            POSIX Programmer's Manual                                           ATOI(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       atoi - convert a string to an integer

SYNOPSIS
       #include <stdlib.h>

       int atoi(const char *str);


DESCRIPTION
       The call atoi(str) shall be equivalent to:


              (int) strtol(str, (char **)NULL, 10)

       except that the handling of errors may differ. If the value cannot be represented, the behavior is undefined.

RETURN VALUE
       The atoi() function shall return the converted value if the value can be represented.

ERRORS
       No errors are defined.

       The following sections are informative.

EXAMPLES
   Converting an Argument
       The  following example checks for proper usage of the program. If there is an argument and the decimal conversion of this
       argument (obtained using atoi()) is greater than 0, then the program has a valid number of minutes to wait for an event.


              #include <stdlib.h>
              #include <stdio.h>
              ...
              int minutes_to_event;
              ...
              if (argc < 2 || ((minutes_to_event = atoi (argv[1]))) <= 0) {
                 fprintf(stderr, "Usage: %s minutes\n", argv[0]); exit(1);
              }
              ...

APPLICATION USAGE
       The atoi() function is subsumed by strtol() but is retained because it is used extensively in existing code. If the  num-
       ber is not known to be in range, strtol() should be used because atoi() is not required to perform any error checking.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       strtol(), the Base Definitions volume of IEEE Std 1003.1-2001, <stdlib.h>

COPYRIGHT
       Portions  of  this  text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for
       Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6,  Copy-
       right (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any
       discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open  Group
       Standard   is   the   referee   document.   The   original   Standard   can   be   obtained  online  at  http://www.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                      ATOI(3P)